The combination of horizontal drilling and fracking has caused an oil boom across the United States. Most notably, the Bakken oil field of North Dakota has grown tremendously in recent years. Flaring from crude oil operations in the Bakken has become an enormous economic and environmental issue. Horizontal drilling and fracking co-produces natural gas. The co-produced gas is normally compressed and sent down a pipeline. However, in the Bakken, the pipeline infrastructure has failed to keep pace with drilling. Consequently, the associated natural gas is often flared. The 2700 wells that are flaring gas in the Bakken have created a problem so severe that it can be seen from space. Legislation to curtail flaring in the Bakken will limit oil production unless flaring alternatives are developed.
There are several known alternatives to flaring. First, lean natural gas—gas that has a small amount of propane and heavier hydrocarbons—can be used as a fuel for an internal combustion engine that, in turn, drives an electrical generator. The generated electricity can be used for local power or sold to the electrical grid. Second, the natural gas can be liquefied to form Liquefied Natural Gas (LNG). Third, natural gas can be compressed and sold as Compressed Natural Gas (CNG). Fourth, natural gas can be converted to liquid fuel including methanol. However, the associated gas produced from horizontal drilling and shale basins is rich gas, because the gas contains substantial amounts of heavier hydrocarbons including propane, butane, hexane, heptane and octane. The aforementioned hydrocarbons are known as Natural Gas Liquid (NGL).
Rich gas is unsuitable for the aforementioned flaring alternatives for three reasons. First, the heavier hydrocarbons cause the gas energy content to be too high for internal combustion. Specifically, the high energy content causes internal combustion engines to knock. Second, the heavier hydrocarbons in the rich gas interfere with methanol and other liquid fuel chemistry. Third, heavy hydrocarbons cause the LNG to be unsuitable for motor-fuel use.